The subject matter disclosed herein relates to an aircraft tail rotor system and, more particularly, to an aircraft tail rotor system including a pitch change shaft bearing assembly.
In many current helicopters or rotary machines (hereinafter “aircraft”), a helicopter tail rotor (TR) system converts tail driveshaft rotary power into the aerodynamic forces necessary to control the direction of flight and to counteract main rotor torque.
A tail rotor head system provides a mounting point for tail rotor blades (TRBs) and for a blade pitch change mechanism. The pitch of the TRBs is controlled by the position of the tail rotor pitch change shaft (PCS) and positioning of the PCS is controlled by a pitch change servo. When the pitch change servo pulls the PCS inboard, the pitch beam and pitch change links twist the TRBs about internal elastomeric bearings to increase blade pitch. Conversely, when the pitch change servo permits the PCS to move outboard, the pitch beam and pitch change links twist the TRBs about internal elastomeric bearings to decrease blade pitch. An increase in blade pitch will turn the aircraft direction to the left and a decrease in pitch will turn the aircraft direction to the right.
The PCS rotates with and moves linearly within a rotating TR shaft. A PCS bearing supports the PCS within the TR shaft and allows the PCS and TR shaft to rotate independently of the non-rotating pitch change servo rod. The PCS bearing outer raceway rotates with the PCS and the TR shaft, while the inner raceway is non-rotating but moves linearly with the pitch change servo rod.